Epoxy adhesives metals

Epoxy resins are also used in special appHcations, such as an overlaying procedure requiring a durable, heat-resistant bond of a difficult-to-bond overlay on a wood-base panel substrate. Metal sheets used as overlays, for example, often require an epoxy adhesive. 

Though toughened phenolic adhesives remain in use for specific applications, toughened epoxy adhesives have dominated metallic bonding on civil aircraft since their development in the 1960s. Advances since then have been incremental and mostly revolving around manufacturing issues such as handleability and allowed out-time. 

The corrosion resistance and polymer-bonding compatibilities of the lonizable organophosphonates and the neutral organo-silanes are directly related to their inherent chemical properties. Specifically, NTMP inhibits the hydration of AI2O2 and maintains or Improves bond durability with a nitrile-modified epoxy adhesive which is cured at an elevated temperature. The mercaptopropyl silane, in addition to these properties, is compatible with a room temperature-cured epoxy-polyamide primer and also exhibits resistance to localized environmental corrosion. These results, in conjunction with the adsorbed Inhibitor films and the metal substrate surfaces, are subsequently discussed. 

The ionic phosphonates like NTMP are effective hydration inhibitors because they can form an insoluble complex with the oxide surface. They are useful as epoxy adhesive couplers in cases where the adhesive and its curing cycle are compatible with the adsorbed phosphonate molecule. (14) Wedge test results indicate that in two epoxy-aluminum systems studied, certain organosilanes tend to both increase the epoxy-metal bond durability and maintain hydration resistance. The results of anodic polarization experiments further suggest that these silane films are effective against localized pitting. 

Methods Used to Increase the Dnrability of Metal/Epoxy Adhesion Systems 50... 

Since, in general, factors which influence the adhesion of metal/epoxy resin structural joints also influence adhesion in metal/epoxy resin protective coating systems, these two separate cases will often be combined and referred to simply as metal/epoxy adhesion systems. 

Displacement of epoxy by water definitely plays an important role in the strength loss of metal/epoxy adhesion systems. However, there are also other mechanisms by which water can reduce the strength of the interfacial region. 

On the other hand, new combined coupling agent — corrosion inhibitor pretreatment processes 29 125 have provided a new approach to increasing metal/epoxy adhesion systems with limits that are not yet known. 

Failure can occur in metal/epoxy adhesion systems in any one or more of a number of different regions. The fracture may propagate through the bulk metal or epoxy, the metal oxide layer, the metal oxide/epoxy or metal/metal oxide interfaces, or through weak boundary layers (WBL s) very near the interfaces. Some workers -78,153) be]ieve that most failures that have been claimed to be interfacial have actually... 

It is important to remember that this review presents the major factors which influence metal/epoxy adhesion systems in general. As a result, one must realize that additional factors may have to be considered when investigating a specific metal/epoxy adhesion system. 

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